Material stack for leds with a dome

Abstract

Various embodiments include methods for forming domed light-emitting diode (LED)-modules and devices constructed by those methods. In one example, the domed LED-module includes a package substrate, an LED die formed on the package substrate, one or more silicone pads formed on the package substrate and at least partially surrounding the LED die, and a high refractive-index material formed over the one or more silicone pads. Other devices and methods are described.

Description

TECHNICAL FIELD[0001]The subject matter disclosed herein relates to a light-emitting diode (LED), a means to mount the LED to a substrate, and a stack of materials to form an encapsulating dome over the LED, thereby forming a domed LED-module. More specifically, the disclosed subject matter relates to a technique to form a material-stack proximate to an LED, along with a dome to both protect the LED and direct a radiation pattern of the LED. The disclosed subject matter further reduces or eliminates cracking and / or delamination problems frequently associated with using the domed LED-module.BACKGROUND[0002]In a light-emitting diode (LED) device, an LED element is frequently encapsulated so as to be protected from, for example, physical impact as well as direct a radiation pattern of the LED. In general, forming a resin over the LED element may serve as a form of encapsulating. For example, an epoxy resin, a silicone resin, or similar materials known in the art may be used. However, t...

AI Technical Summary

Benefits of technology

The patent text describes a technique for making a domed LED-module that includes an LED element protected from physical impact and directing its radiation pattern. The technique involves forming a material-stack over the LED, including a dome to both protect the LED and direct its radiation pattern. This technique reduces or eliminates cracking and delamination failures often associated with using conventional materials. The patent also includes examples of the use of the technique in various applications. Overall, the patent provides a solution for improving the reliability and performance of domed LED-modes.

Problems solved by technology

However, there is typically a mismatch between the thermo-mechanical properties of such materials and the substrate onto which they are disposed or otherwise formed, which can lead to cracking and delamination related failures.

However, a shape of the dome, and the material used to form the dome, can have detrimental effects on an overall reliability of the LED package, particularly when the dome-height to package-width aspect ratio becomes large.

However, phenyl silicones with a high refractive-index generally cannot perform well in low temperature applications or in thermal-cycling reliability tests where the package is repeatedly transferred between temperatures from, for example, −40° C. to 125° C. or from −55° C. to 150° C. Industry-standard tests typically involve temperature ranges of −40° C. to 125° C. for purposes of product qualification and temperature ranges of −55° C. to 150° C. for purposes of overstress testing.

In the worst case, the delamination can propagate to the LED chip and / or wire bonds resulting in a loss of function of the LED itself, resulting in no light being output from the package.

However, the dimethyl silicones cannot match the light output achieved using silicones with a high refractive-index material of, for example, 1.53 and above.

As mentioned above, the domes of the packages with high-aspect ratios, such as bullet-shaped domes, which are used for some optical features of the LED packages, have some limitations in reliability tests.

), which means phenyl silicones generally cannot perform well in temperature reliability tests which need to transfer the condition of the packages from about −40° C. to about 125° C. Usually, the domes with certain aspect ratios of the dome delaminate from the substrates onto which the domes are moulded.

However, as noted above, the dimethyl silicones cannot match the light output that can be achieved with the silicones (e.g., phenyl silicones) having high refractive-indices of about 1.5 and above.

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